Braking band, a ventilated disk-brake disk, and a core box for the production of a disk-brake disk core

ABSTRACT

A braking band with a remarkable capacity for improved cooling, for use in disk-brake disks, comprises two plates coaxial with an axis, facing one another, and spaced apart to form a space in which an air-flow takes place from the axis towards the outer side of the band, the plates having facing surfaces from which pillar-like elements extend, transversely, to connect the plates, the pillar-like elements being distributed in circular rings or rows concentric with the plates so as to be distributed uniformly in the space, those pillar-like elements which are disposed in inside rows of the braking band having rhombic cross-sections. The rhombic cross-sections of the pillar-like elements which are in inside rows of the band are symmetrical with respect to an axis transverse the direction of flow and each element for connection between the plates extends from one plate to the other whilst remaining within the space.

[0001] The present invention relates to a braking band and to aventilated disk-brake disk, particularly but not exclusively forapplications in the automotive field.

[0002] A further aspect of the present invention relates to a core boxfor the production of a disk-brake disk core.

[0003] As is known, a disk of the type specified above is constituted bytwo coaxial portions. A first portion, the support bell, is forconnection to the wheel hub of a vehicle, and the remaining, peripheralportion, the so-called braking band, is for cooperating with thedisk-brake calipers in order to exert the braking force on the vehicle.

[0004] More particularly, the present invention relates to a so-calledventilated disk, that is, a disk in which the braking band isconstituted by two facing, coaxial plates, spaced apart so as to form aspace. The two plates are connected by pillar-like elements which extendthrough the space between the two plates. Ventilation ducts are thuscreated between the plates and air flows through the ducts in adirection from the inner side of the braking band towards the outerside, thus helping to dissipate to the environment the heat generated inthe band upon each braking operation.

[0005] Pillar-like elements of various shapes, of various sizes, anddistributed variously around the space in the braking band are known.Disk-brake disks in which the pillar-like elements are in a quincuncialarrangement and in three rows are known. Moreover, the shape of thecross-section of each pillar-like element, taken in an areasubstantially parallel to the direction of the air-flow through thespace, varies from row to row. In particular, the elements of the innerrow have a cross-section which is tapered towards the outer side of thebraking band.

[0006] A disk of this type is described, for example, in U.S. Pat. No.4,865,167.

[0007] Disks with pillar-like elements of different radial extent, whichare rounded towards the interior of the braking band are also known. Adisk of this type is described, for example, in U.S. Pat. No. 6,152,270.

[0008] Other disks provided with pillar-like elements are known fromEP-A-0318687, EP-A-0989321, and DE-A-4210449.

[0009] Although these known disks are satisfactory from some points ofview, they have considerable disadvantages.

[0010] First of all, poor ventilation efficiency or, in other words, apoor cooling capacity has been noted, due to the resistance offered tothe flow of air inside the space present in the braking band, whichresistance is caused by the known shape of the elements connecting theplates.

[0011] Moreover, poor resistance of the braking band to thermal stressesand, in some extreme cases, to mechanical stresses has been noted, thispoor resistance being caused mainly by the known geometrical arrangementof the elements connecting the plates.

[0012] As is also known, disk-brake disks are produced by casting andthe ventilation ducts between the two plates are formed during casting,with the use of a core. The core in turn is formed by the injection ofcore sand, that is, an agglomerate of sand and resins, into a core box.

[0013] The latter is constituted by two half-shells which, when coupled,define inside them a cavity which reproduces, amongst other things, theinternal structure of the disk and, in particular, the space between thetwo plates. The two half-shells consequently have projecting elementsfor defining cavities in the core which, when the disk is cast will formthe pillar-shaped elements connecting the two plates.

[0014] During the production of the core, the core sand is injected intothe two coupled half-shells by being made to flow from the innermostdiameter to the outermost diameter. When the sand starts to flow throughthe cavity which will define the space between the two plates, theprojecting elements and, in particular, the inner row, consequentlycause an obstruction to the flow of sand.

[0015] The core-moulding step is therefore critical, because of theabove-mentioned obstructions. In fact, the sand which is in the vicinityof the pillar-like elements of the outermost row and, in particular, inthe region facing outwardly relative to the disk, does not have thenecessary compactness to withstand the casting of the molten metal.During casting, the flow of molten metal may in fact undermine the lesscompact regions of the core and replace them, giving rise to undesiredprotuberances which adversely affect the further processing steps andthe operation of the disk.

[0016] The protuberances may cause obstructions in the first subsequentprocessing step in which the disk is gripped and located by restrainingelements which are inserted in the space between the plates. Moreover,the protuberances may, for example, lead to an imbalance in the massesof the disk so that a larger amount of material has to be removed in thebalancing step at the end of the processing cycle. Finally, when thedisk is in use, the presence of these protuberances may constitute anobstruction to the air-flow through the ventilation ducts, giving riseto disturbances in the flow with a consequent reduction in coolingefficiency. It is clear form the foregoing that, to prevent theabove-mentioned disadvantages, there is a particular requirement in thisfield to achieve a correct degree of compactness in every portion of thecore which will subsequently be used during the casting of a disk-brakedisk.

[0017] The object of the present invention is to devise and to provide abraking band, a ventilated disk-brake disk, and a core box for theproduction of a disk-brake disk core which satisfy the above-mentionedrequirements and, at the same time, prevent the problems mentioned withreference to the prior art.

[0018] This object is achieved by means of a braking band for adisk-brake disk according to claim 1, by means of a ventilateddisk-brake disk according to claim 19, and by means of a core box forthe production of a disk-brake disk core according to claim 22.

[0019] Further characteristics and the advantages of the band, of thedisk, and of the core box according to the invention will become clearfrom the following description of a preferred embodiment thereof, givenby way of non-limiting example with reference to the appended drawings,in which:

[0020]FIG. 1 is a partially-sectioned, perspective view of a disk-brakedisk according to the present invention,

[0021]FIG. 2 is a partially-sectioned, front view of the disk of FIG. 1,

[0022]FIG. 3 is a section through the disk, taken on the line III-III ofFIG. 2,

[0023]FIG. 4 is a section through a possible variant of the disk of FIG.3,

[0024]FIG. 5 is a diametral section through a core box according to thepresent invention,

[0025]FIG. 6 shows the core box of FIG. 5 in a different operativecondition,

[0026]FIG. 7 is a diametral section through a core produced by the corebox of FIGS. 5 and 6,

[0027]FIG. 8 shows, in diametral section, a disk-brake disk at the stageof its production by casting,

[0028]FIG. 9 is a partially-sectioned, perspective view of a detail ofthe core box,

[0029]FIG. 10 is a partially-sectioned, side view of the detail of FIG.9, and

[0030]FIG. 11 is a partially-sectioned, perspective view of a seconddetail of the core box.

[0031] With reference to the above-mentioned drawings, a disk-brake diskaccording to the present invention, in particular, a so-calledventilated disk for use in a disk brake (not shown) of a vehicle such asa motor car, is generally indicated 10. The disk 10 is substantiallycircular and extends about an axis indicated Z-Z in the drawings.

[0032] The disk 10 comprises a support bell 12 and a braking band 14coaxial with the bell 12.

[0033] The braking band 14, which is intended to cooperate with thedisk-brake calipers in order to exert the braking force on the vehicle,comprises a first plate 16 and a second plate 18 arranged coaxially onthe axis Z-Z. The first plate 16 is on the same side as the bell support12 and the second plate 18 is on the opposite side.

[0034] The two plates face one another and are spaced apart to form aspace 20 in which an air-flow takes place from the axis Z-Z towards theouter side of the braking band 14 during the rotation of the disk.

[0035] The two plates have facing surfaces 22 from which pillar-likeelements 24, 26 and 28, also commonly known as pins, extendtransversely.

[0036] The pillar-like elements extend to connect the two plates. Inparticular, the first plate is formed continuously with the support bell12 and the second plate 18 is connected to the first by means of thepillar-like elements.

[0037] The pillar-like elements are distributed uniformly around thefacing surfaces 22 of the plates and, in the embodiment shown, aredivided into three concentric, circular rings or rows corresponding toan inner row, that is, the row closest to the axis Z-Z, an intermediaterow, and an outer row, that is, the row farthest from the axis Z-Z. Forsimplicity of description, the pillar-like elements of the inner row areindicated 24, the pillar-like elements of the intermediate row areindicated 26 and, finally, the pillar-like elements of the outer row areindicated 28. According to one embodiment, the pillar-like elementscomprise more than one intermediate row (intermediate pillar-likeelements 26), for example two intermediate rows disposed between theinner row (the inner pillar-like elements 24) and the outer row (theouter pillar-like elements 28).

[0038] The pillar-like elements 24 of the inner row constitutepillar-like elements which are disposed in the vicinity of the edge ofthe braking band 14 that faces the axis Z-Z. The cross-section of eachof these pillar-like elements in an area substantially parallel to thedirection of the air-flow in the space is tapered towards the axis Z-Z.In greater detail, the pillar-like elements have a cross-section whichis tapered both towards the axis Z-Z of the plates and towards the outerside of the braking band 14, forming a substantially rhombiccross-section.

[0039] According to one embodiment, the pillar-like elements 24, 26arranged in inside rows of the band, meaning the inner row and the atleast one intermediate row, have rhombic cross-sections, cross-sectionmeaning a section considered in an area substantially parallel to thedirection of the air-flow through the space 20, as will be describedfurther below.

[0040] The rhombic cross-section is a cross-section which has four atleast partially flat sides. A pillar-like element having a rhombiccross-section is an element which has a lateral surface or wallcomprising four at least partially flat faces suitable for defining aventilation duct of the braking band and suitable for directing theair-flow from the interior towards the exterior of the disk in themanner which will be described in greater detail below.

[0041] According to one embodiment, the pillar-like elements 24, 26 havelinked flat surfaces defining the rhombic cross-section.

[0042] In particular, according to one embodiment, the pillar-likeelements 24, 26 of the inner and intermediate rows have, in a radialdirection, ends with link radii R1 variable from 1.5 mm to 2.5 mm andpreferably 2 mm. The pillar-like elements 28 of the outer row have, in aradial direction, a first end with a link radius R1 variable from 1.5 mmto 2.5 mm and preferably 2 mm, and a second end, preferably the outerend, with a link radius R4 variable from 4 mm to 5 mm and preferably 4.5mm. The pillar-like elements 24 of the inner row have, in a directiontransverse the direction of flow, link radii R2 variable from 3 mm to3.5 mm between the flat surfaces. The pillar-like elements 26 of the atleast one intermediate row have, in a direction transverse the directionof flow, link radii R3 variable from 3.5 to 4 mm between the flatsurfaces.

[0043] Preferably, all of the pillar-like elements 24, 26, 28 areconnected to the plates 16, 18 with link radii R5 variable from 3 mm to4 mm, preferably 3.5 mm (FIGS. 3 and 4).

[0044] Advantageously, the rhombic cross-sections of the pillar-likeelements 24, 26 which are in inside rows of the band 14 are symmetricalwith respect to an axis transverse the direction of flow and eachelement 24, 26, 28 suitable for connection between the plates 16, 18extends from one plate to the other 16, 18, whilst remaining inside thespace 20. In other words, starting from a central portion of maximumtangential extent or largest dimension, a pillar-like element of theinside rows of the band (the inner row, or row closest to the axis Z-Zand the at least one intermediate row) is tapered towards the interiorand towards the exterior of the disk with portions of equal extent andadvantageously together forming pairs of parallel faces arranged fordirecting air in a controlled manner through the ducts or channelsdefined in the space. Moreover, each element which serves for theconnection of the plates does not project or protrude outside the space20, avoiding the formation of elements for diverting the air-flow whichproject from the space to the exterior of the plates. In other words,the inner opening and the outer opening of the space 20 are free ofobstacles to the free circulation of the air-flow.

[0045] With further advantage, the radial ends of the cross-sections ofadjacent rows are substantially aligned on the same circle (FIG. 2). Inother words, between adjacent rows, for example, the inner row and theintermediate row, or the intermediate row and the outer row, there is nooverlap in a tangential direction between the pillar-like elements 24and 26 or 26 and 28 (any circle concentric with the axis Z-Z of theplates 16, 18 and extending through pillar-like elements of one row doesnot extend through pillar-like elements of another row).

[0046] Advantageously, each of the pillar-like elements 24, 26, 28 ofeach row has substantially the same radial extent D in the saidcross-section. In other words, the connecting elements of the plates areconnecting areas for the plates, and hence also stiffening areas, whichare distributed uniformly over the extent of the plates as a whole.

[0047] Advantageously, the pillar-like elements 24, 26, 28 interconnectthe plates 16, 18 over an area no greater than 15%-25%, preferably 20%of the total facing surface area of each plate. In other words, thefacing plates, which have an overall inner lateral surface area(substantially equal to an outer surface area suitable for interactingwith pads of a braking system or braking surface), are covered by theconnecting elements over an area variable from 15% to 25% and preferably20% of the overall area of the facing surface.

[0048] According to one embodiment, the two plates 16, 18 are connectedby pillar-like elements 24, 28 disposed along at least one inner row andone outer row which are concentric with one another.

[0049] According to a further embodiment, one or two furtherintermediate rows of pillar-like elements 26 are provided.

[0050] Preferably, the pillar-like elements 26 of the at least oneintermediate row are offset relative to those 24, 28 of the inner andouter rows.

[0051] With further advantage, the pillar-like elements 24, 26, 28 aredistributed between the two plates 16, 18 in a quincuncial arrangement.

[0052] The dimensions of the pillar-like elements may vary on the basisof the vehicle for which the disk is intended. For example, thedimension in the circumferential direction, that is, the shorterdiagonal d of the rhombus, has a value which is variable in dependenceon the type of vehicle, for example, 6 mm for a motor car or 10-12 mmfor a commercial vehicle, whereas the dimension in a radial direction,that is, the longer diagonal D, has a value which depends on the width hof the braking band, meaning the difference between the outside radiusand the inside radius of the braking band. The sides of the rhombiccross-section are linked together.

[0053] According to one embodiment, the pillar-like elements 24 of theinner row have, in an area substantially parallel to the direction ofthe air-flow through the space 20, a diagonal of the rhombiccross-section transverse the direction of flow having dimensions ofbetween 6 mm and 7 mm.

[0054] According to a further embodiment, the pillar-like elements 26 ofthe at least one intermediate row have, in an area substantiallyparallel to the direction of the air-flow through the space 20, adiagonal of the rhombic cross-section transverse the direction of flowhaving dimensions of between 7 mm and 8 mm.

[0055] This cross-section is shown, by way of example, in FIG. 2 whichis a front view of the disk and of the braking band in which the secondplate 18 has been partially sectioned to show the shapes of thepillar-like elements of the at least three rows. This cross-sectiontherefore corresponds to the above-mentioned area substantially parallelto the direction of the air-flow through the space and may correspond toa plane transverse the axis Z-Z of the disk, or to an arcuate area, independence on the shapes adopted by the two plates and by the space.

[0056] The cross-section of each of the pillar-like elements 28 of theouter row in an area substantially parallel to the direction of theair-flow through the space is drop-shaped. In particular, thiscross-section is tapered towards the axis Z-Z of the plates and has anouter link portion, for example, with a radius of 5 mm.

[0057] Moreover, the cross-section of each of the pillar-like elements26 of the intermediate row in an area substantially parallel to thedirection of the air-flow through the space is tapered both towards theaxis Z-Z of the plates and towards the outer side of the braking band.The pillar-shaped elements of the intermediate row thus also have asubstantially rhombic cross-section similar to that of the pillar-likeelements of the inner row.

[0058] The following are some possible definitions of the areasubstantially parallel to the direction of the air-flow through thespace.

[0059] The embodiment of FIG. 3 in fact has a disk in which the twoplates constituting the braking band are substantially parallel toplanes perpendicular to the axis Z-Z and the space 20 correspondinglyextends in a ring coaxial with the axis Z-Z. The connection between thefirst plate 16 and the bell 12 is formed between walls which aresubstantially perpendicular to one another, although they are suitablylinked. In this configuration, the facing surfaces 22 of the two platesextend in two planes from which the pillar-like elements 24-28 projectperpendicularly. According to this embodiment, the air-flow enters thespace 20 in the vicinity of the region closest to the axis Z-Z andpasses through it towards the outer side of the braking band. As aresult, an area substantially parallel to the direction of the air-flowthrough the space 20 could be constituted by the median plane of thespace, indicated by a line 30 in FIG. 3.

[0060] The example of FIG. 4 shows a further embodiment of the disk inwhich, with respect to the axis Z-Z, an outer portion of the first plate16 is substantially parallel to planes perpendicular to the axis Z-Z,whereas an inner portion of the first plate 16 deviates, curving towardsthe second plate 18. The space 20 correspondingly extends in a ringcoaxial with the axis Z-Z at least in the outer portion of the bandwhereas, in the region of the deviation of the first plate 16, the spacedeviates away from the bell. In fact, the connection between the firstplate 16 and the bell is formed between walls which are substantiallyinclined to one another and suitably linked. In this configuration, thesurface 22 of the second plate 18 extends in a plane perpendicular tothe axis Z-Z, whereas the surface 22 of the first plate has a curvedshape. The three rows of pillar-like elements are distributed over theentire extent of the braking band. In particular, the innermost row,indicated by the pillar-like elements 24, also follows the shape of thearcuate portion of the space, by virtue of its shape, tapered towardsthe inner side of the braking band. In an embodiment of this type, theair-flow enters the space in the vicinity of the region closest to theaxis Z-Z, which is arranged almost facing the front of the disk, andpasses through the space towards the outer side of the band. As aresult, an area substantially parallel to the direction of the air-flowthrough the space could be constituted, for example, by the central areaof the space, which is indicated by a line 32 in FIG. 4.

[0061] In the embodiment shown, with reference, for example, to FIG. 2,the pillar-shaped elements of the intermediate row are offset relativeto those of the inner row and of the outer row. In particular, thepillar-like elements 24, 26 and 28 are distributed between the twoplates in a quincuncial arrangement.

[0062] Moreover, as shown in FIGS. 1 to 4, the bell 12 and the brakingband 14 are formed as a single element, produced by casting, in whichthe braking band extends continuously from the support bell.

[0063] The connecting portion between the bell and the braking band mayadopt different configurations two of which are shown, for example, inFIGS. 3 and 4, as described above.

[0064] As will be appreciated from the foregoing description, by virtueof the provision of a braking band provided with plates connected bypillar-like connection elements which are disposed entirely within thespace and, in the case of the pillar-like elements of the inside rows,are of symmetrical rhombic shape, it is possible to overcome thedisadvantages of the disks of the prior art and, in particular, aremarkable improvement has been found in the air-flow through theventilation ducts or channels of the space.

[0065] Moreover, as will be appreciated from the foregoing description,by virtue of the provision of a braking band having plates connected bypillar-like connecting elements disposed in adjacent rows in which theradial ends of the cross-sections are substantially aligned on the samecircle, and in which each of the pillar-like elements 24, 26, 28 of eachrow has substantially the same radial extent in the said cross-section,it is possible to overcome the disadvantages of the disks of the priorart and, in particular, a remarkable improvement has been found in theresistance of the braking band, for example, to the large stressescaused by considerable thermal gradients, as well as a low incidence ofsplitting or cracking in the plates even when they are stressed bysevere and repeated braking operations.

[0066] A comparison of tests on the behaviour of the air-flow in aventilation duct or channel provided in the space between two plates ofa disk having a geometrical arrangement according to the prior art and adisk having a geometrical arrangement according to the present inventiondemonstrates the remarkable improvement in the ventilation achieved bythe geometrical arrangement of the solution proposed herein. Inparticular, it is possible to evaluate the vector field of the velocityof the air-flow which passes through a portion of space of a known diskand of the disk having the geometrical arrangement resulting from thesolution proposed herein, which field is repeated circumferentiallythroughout the space. The comparative test between the known geometricalarrangement and that of the solution proposed herein was carried out bya computational fluid-dynamics program, by setting as conditions,rotation of the disk at 1500 rpm (revolutions per minute), an ambientpressure at the input and output of the space, and a temperature of 20°C. By this test it was possible to compare the vector fields and toconclude that the air-flow in the solution proposed herein was moreuniform, both at the input to the space and at the output therefrom, andpassed around the pillar-like elements much better or, in other words,was diverted less by the impact against the pillar-like elements. From aquantitative comparison, it was found that the maximum velocity reachedby the air in the solution proposed herein was slightly reduced incomparison with the maximum velocity of the known solution, in favour ofa considerable increase in the minimum air velocity, consequentlyleading to an improvement or increase in the volume flow (in litres persecond of air) of more than 5% in comparison with the flow-rate of theknown disk.

[0067] Further Advantages of the Solution Proposed are:

[0068] the proposed transverse extent of the elements of the inner andintermediate rows (the inside rows of the band) enables improved controlof the air-flow in the space to be achieved,

[0069] the lack of overlap or space between the adjacent rows rendersthe local stiffness of the entire disk homogeneous, avoiding thedisadvantage which is present in the case of overlap (although small) ofconnection elements of adjacent rows or, in other words, avoidingcircular portions which have twice as many connection elements as otherportions, and thus avoiding regions of the band having non-homogeneousstiffness,

[0070] the provision of connecting elements having symmetrical rhombiccross-sections permits an improvement in ventilation efficiency and, inparticular, an increase in the air-flow which passes through the spaceper unit of time,

[0071] by virtue of the proposed link radii between the flat surfaces ofthe connecting elements, the achievement of a remarkable compromisebetween the provision of sharp corners and excessively rounded elementswhich, in both cases, would adversely affect the controlledtransportation of the air; in particular, the proposed radius linkingthe pillar-like elements and the plates avoids angles which aredifficult to achieve and a cross-section which is inadequate for thedesired air-flow,

[0072] by virtue of the proposed percentage of the total facing surfacesof the plates which is covered by the connecting elements, it ispossible to achieve a remarkable resistance to cracking of the brakingsurface, permitting a controlled resistance to thermal expansion of theplates which are stressed by the braking action, and

[0073] low weight of the disk.

[0074] The main steps of the production of the disk according to thepresent invention by casting are illustrated in FIGS. 5 to 8. FIGS. 5and 6 show a core box 34 comprising a half-shell 36 to be arranged ontop and a half-shell 38 to be disposed at the bottom. In FIG. 5, the twohalf-shells are separated whereas, in FIG. 6, they are coupled and acavity 40 is defined inside them.

[0075] The upper half-shell 36 has a substantially circular structureextending about an axis X-X. In a central position concentric with theaxis X-X, there is a duct 42 for the core sand which, by occupying thecavity 40, will give rise to a core 44, for example, shown in FIG. 7.

[0076] At least a portion of an inner surface 37 of the above-mentionedhalf-shell follows-substantially the shape of the inner surface of thefirst plate 16 and of the bell 12. In particular, it can be seen thatthe profile concerned is of the type shown in FIG. 4, that is, a profilein which the first plate 16 has a flat portion and an arcuate portiondisposed in the vicinity of the bell.

[0077] The lower half-shell 38 also has a substantially circularstructure extending about the axis X-X. In a central position,concentric with the axis X-X, there is a cylindrical protuberance 46facing the duct 42 of the upper half-shell 36.

[0078] In the lower half-shell 38 as well, at least a portion of aninner surface 38 substantially follows the shape of a portion of thedisk and, in particular, of the inner surface of the second plate 18.

[0079] When the two half-shells are coupled, as shown in FIG. 6, theperipheral portion of the cavity 40 has the structure of a ring 48 whichhas a depth greater than that of the adjoining portion of the cavity andcan give rise to a core portion 50 which extends peripherally relativeto the core.

[0080] With reference to FIG. 6, a region of the cavity 40 which, in thesubsequent steps of the process will give rise to the space in thebraking band, that is, the region substantially interposed between theannular ring 48 and the protuberance 46, is indicated 51. Projectingelements 52, 54 and 56, the shape and distribution of which depends onthe shape and the distribution of the pillar-like elements 24-28 of thedisk, extend through this region.

[0081] In particular, the projecting elements 52 are such as to form inthe core 44 corresponding cavities which in turn can give rise to thepillar-like elements 24 of the inner row of the disk 10. Similarly, theprojecting elements 54 are such as to form in the core 44 correspondingcavities which in turn can give rise to the pillar-like elements 26 ofthe intermediate row and, finally, the projecting elements 56 are suchas to form in the core 44 corresponding cavities which in turn can giverise to the pillar-like elements 28 of the outer row.

[0082] Consequently, in an area parallel to the direction of flow ofsand through the cavity 40, the projecting elements 52-56 havecross-sections similar to the cross-sections of the respectivepillar-shaped elements 24-28. As shown in FIGS. 5, 6, 10 and 1, theprojecting elements 54 and 56 extend through a portion of the depth ofthe cavity 40 between the two half-shells equal to approximately half ofthis depth. In fact, the projecting elements 54 and 56 of one half-shellhave a surface 58 for contact with the respective projecting elements 54and 56 of the other half-shell.

[0083] It is also clear from FIGS. 5, 6, 10 and 11 that the projectingelements 52 corresponding to the inner row of pillar-like elements 24are associated with only one of the two-half-shells, that is, in theembodiment in question, with the upper half-shell 36, and extend throughthe entire depth of the cavity 40 between the two half-shells,contacting the inner surface 39 of the lower half-shell 38 directly. Inparticular, it is clear from FIG. 10 that the height of the projectingelements 52 is greater than that of the projecting elements 54 and 56which is in fact approximately half that of the projecting elements 52.

[0084] This configuration allows the two half-shells 36 and 38 to beopened along the axis X-X in order to remove the core 44 from the mould,even when the connecting portion between the braking band 14 and thebell 12 is arcuate, as shown, for example, in FIG. 4. In fact, theconfiguration of the disk 10 is reproduced in similar manner in theinner surfaces 37 and 39 of the core box 34 and the presence ofprojecting elements 52 integral with the upper half-shell 36 avoids thepresence of undercuts.

[0085] The method for the production of a disk as described above, andconsequently the ways in which a core box and a core as described aboveare used, are described below. FIG. 5 shows the two half-shells at thestage in which they are brought together along the axis X-X. When thetwo half-shells are coupled as shown in FIG. 6, core sand is sent intothe cavity 40 defined by the two half-shells, through the duct 42. Thecore sand is an agglomerate of sand and resins which polymerize as aresult of the heating of the walls of the core box.

[0086] The particular shape of the projecting elements 52, the shape ofwhich depends on the shape of the pillar-like elements 24, favours theflow of sand into the core box and ensures that the compactnessnecessary for the subsequent success of the casting is achieved even inthe peripheral regions of the braking band.

[0087] The sand in fact maintains a high velocity up to the periphery ofthe core and this is influenced positively by the taper of theprojecting elements 52 (corresponding to the pillar-like elements 24)which limit disturbances in the flow of sand.

[0088] When the sand has been compacted, the two half-shells are removedin the directions defined by the axis X-X and the core 44 is removedfrom the mould and is as shown in FIG. 7.

[0089] The core 44 is then inserted in a mould formed in sand for thecasting of the disk 10.

[0090] It can be appreciated from the foregoing that the provision forthe pillar-shaped elements 24 disposed in the vicinity of the edge ofthe braking band that faces towards the axis Z-Z to have a cross-sectiontapered towards the axis Z-Z and, in particular, tapered in bothdirections to form a rhombic cross-section in an area substantiallyparallel to the direction of the air-flow through the space, isparticularly advantageous.

[0091] A configuration of this type is in fact reflected in a similarconfiguration of the projecting elements 52 and hence in a optimaldegree of compactness of the core used for the casting of the disk.

[0092] The fact that it is possible to use a core having optimalcharacteristics of compactness consequently affects the quality of thedisk produced and reduces subsequent processing. In particular, themasses of the disk are uniformly distributed and the step of thebalancing of the masses of the disk is less onerous, particularly withregard to the amount of mass removed. Moreover, the advantageousconfiguration of the core box, and consequently of the core, permit theproduction of a disk which, throughout the space 20, is substantiallyfree of imperfections or blockages which would adversely affect theair-flow therein.

[0093] The presence of an inner row of pillar-like elements 24 such asthose described above enables the presence of the pillar-like elementsalso to be extended to the vicinity of the bell, particularly inembodiments which provide for a deviation of the first plate 16 and ofthe space 20 as shown, for example, in FIG. 4.

[0094] In these conditions, the presence of the projecting elements 52enables the core to be removed easily from the core box by avoidingundercuts.

[0095] Moreover, the above-described arrangement is particularlyadvantageous, for example, for disks in which the bell and the banddefine a single element. In this case, owing to the shape which the diskwill have to adopt, the passageway for the core sand through the cavitymay in fact be particularly tortuous because of the presence of acontinuous wall between the bell and the braking band. Theabove-described arrangement may also be advantageous for disks in whichthe braking band is connected to the bell by means of connectingelements having a first end fixed to the braking band and a second endassociated slidably with the bell. In this case, in fact, the flow ofsand along the core box may also be tortuous and subject to turbulencewhich would limit the compactness of the core, particularly in theregions which face the outer side of the band in the region of the outerrow of projecting elements 56 corresponding to the pillar-like elements28.

[0096] Naturally variants and/or additions may be provided for theembodiments described and illustrated above. The arrangement of thepillar-like elements and of the corresponding projecting elements mayvary. In this case, the advantageous configuration of the pillar-likeelements of the inner row, as described above, applies to any of thepillar-like elements which are disposed in the vicinity of the edge ofthe braking band facing the axis Z-Z. These pillar-like elementscorrespond to the projecting elements which are reached first by theflow of core sand during the formation of the core 44.

[0097] Naturally, the number of pillar-like elements and the shape ofthe cross-sections of the elements of the outer row and of theintermediate row or, in any case, of the pillar-like elements which arenot disposed in the vicinity of the edge of the braking band facing theaxis Z-Z, may vary.

[0098] In order to satisfy contingent and specific requirements, aperson skilled in the art may apply to the above-described preferredembodiment of the braking band, of the disk, and of the core box manymodifications, adaptations and replacements of elements with otherfunctionally equivalent elements without, however, departing from thescope of the appended claims.

1. A braking band (14) for a disk-brake disk (1Q) comprising two plates(16, 18) coaxial with an axis (Z-Z), facing one another, and spacedapart to form a space (20) for an air-flow from the axis (Z-Z) towardsthe outer side of the band (14), the plates (16, 18) having facingsurfaces (22) from which pillar-like elements (24, 26, 28) extend,transversely, to connect the plates (16, 18), the pillar-like elements(24, 26, 28) being distributed in circular rings or rows concentric withthe plates (16, 18) so as to be distributed uniformly in the space (20),those pillar-like elements (24, 26) which are disposed in inside rows ofthe band having rhombic cross-sections, the cross-sections beingconsidered in an area substantially parallel to the direction of theair-flow through the space (20), characterized in that the rhombiccross-sections of the pillar-like elements (24, 26) which are in insiderows of the band (14) are symmetrical with respect to an axis transversethe direction of flow, and in that each element (24, 26, 28) suitablefor connection between the plates (16, 18) extends from one plate to theother (16, 18) whilst remaining within the space (20).
 2. A braking bandaccording to claim 1 in which radial ends of the cross-sections ofadjacent rows, considered in an area substantially parallel to thedirection of the air-flow through the space (20), are substantiallyaligned on a common circle.
 3. A braking band according to claim 1 orclaim 2 in which each of the pillar-like elements (24, 26, 28) of eachrow has substantially the same radial extent in the said cross-section.4. A braking band according to at least one of the preceding claims inwhich the pillar-like elements (24, 26, 28) interconnect the plates (16,18) over an area no greater than 15%-25%, preferably 20% of the totalfacing surface area of each plate.
 5. A braking band according to atleast one of the preceding claims in which the pillar-like elements (24,26) have linked flat surfaces delimiting the rhombic cross-sections. 6.A braking band according to at least one of the preceding claims inwhich the two plates (16, 18) are connected by pillar-like elements (24,28) disposed along at least one inner row and one outer row which areconcentric with one another.
 7. A braking band according to claim 0.6 inwhich the pillar-like elements (28) of the outer row have asubstantially drop-shaped cross-section in an area substantiallyparallel to the direction of the air-flow through the space (20).
 8. Abraking band according to claim 7 in which the substantially drop-shapedcross-section of the pillar-like elements (28) of the outer row istapered towards the axis (z-Z) of the plates (16, 18).
 9. A braking bandaccording to at least one of claims 6 to 8 in which one or two furtherintermediate rows of pillar-like elements (26) are provided.
 10. Abraking band according to at least one of the preceding claims in whichthe pillar-like elements (24) of the inner row have, in an areasubstantially parallel to the direction of the air-flow through thespace (20), a diagonal of the rhombic cross-section transverse thedirection of flow having dimensions of between 6 mm and 7 mm.
 11. Abraking band according to at least one of the preceding claims in whichthe pillar-like elements (26) of the at least one intermediate row have,in an area substantially parallel to the direction of the air-flowthrough the space (20), a diagonal of the rhombic cross-sectiontransverse the direction of flow having dimensions of between 7 mm and 8mm.
 12. A braking band according to at least one of the preceding claimsin which the pillar-like elements (26) of the at least one intermediaterow are offset relative to those (24, 28) of the inner row and of theouter row.
 13. A braking band according to at least one of the precedingclaims in which the pillar-like elements (24, 26, 28) are distributed ina quincuncial arrangement between the two plates (16, 18).
 14. A brakingband according to at least one of the preceding claims in which thepillar-like elements (24, 26) of the inner and intermediate rows have,in a radial direction, ends with link radii variable from 1.5 mm to 2.5mm, preferably 2 mm.
 15. A braking band according to at least one of thepreceding claims in which the pillar-like elements (28) of the outer rowhave, in a radial direction, a first end with a link radius variablefrom 1.5 to 2.5 mm, preferably 2 mm, and a second end with a link radiusvariable from 4 mm to 5 mm, preferably 4.5 mm.
 16. A braking bandaccording to at least one of the preceding claims in which thepillar-like elements (24) of the inner row have-, in a directiontransverse the direction of flow, link radii variable from 3 mm to 3.5mm between the flat surfaces.
 17. A braking band according to at leastone of the preceding claims, in which the pillar-like elements (26) ofthe at least one intermediate row have, in a direction transverse thedirection of flow, link radii variable from 3.5 mm to 4 mm between theflat surfaces.
 18. A braking band according to at least one of thepreceding claims in which the pillar-like elements (24, 26, 28) areconnected to the plates (16, 18) with link radii variable from 3 mm to 4mm, preferably 3.5 mm.
 19. A disk-brake disk (10) comprising a brakingband (14) according to any one of the preceding claims.
 20. A disk-brakedisk according to claim 19 in which the braking band (14) does not haveelements for connection to a bell (12) which have a first end fixed tothe braking band (14) and a second end associated slidably with the bell(12).
 21. A disk-brake disk according to claim 19 in which a plate (16)of the braking band (14) is connected to a bell (12).
 22. A core box(34) for the production of a core (44) for a disk-brake disk (10),comprising two half-shells (36, 38) which, when coupled, define a cavity(40), and of which at least one has elements (52) projecting towards theother through the cavity (40) to produce in the core (44) cavities forforming pillar-like elements (24) which extend to connect plates (16,18) constituting a braking band (14) of the disk, as defined in any oneof claims 1 to
 18. 23. A core box according to, claim 22 in which theprojecting elements (52) are distributed around a circular ring or rowconcentric with the respective half-shell (36).
 24. A core box accordingto claim 23 in which each of the two half-shells (36, 38) comprisesfurther projecting elements (54, 46) which extend through a portion ofthe depth of the cavity (40) between the two half-shells.
 25. A core boxaccording to claim 24 in which the further projecting elements (54, 56)of one half-shell have a surface (58) for contact with respectivefurther projecting elements (54,56) of the other half-shell.
 26. A corebox according to claim 24 or claim 25 in which the further projectingelements (54, 56) are distributed around at least one circular ring orrow concentric with the respective half-shell.